I don't know if this is a bug or not but Minecraft is having some sort of unexpected error and keeps closing when I try to log onto a server. Please help!

Minecraft crashes when I try to join a server of some kind and the description in the launcher says "Unexpected Error" and I'm getting very frustrated. If this happens again, I'll just stop playing Minecraft until it says on the Update Notes that it is fixed.

P.S. I'm only 11!